Horizontal convergence circuit

ABSTRACT

A horizontal convergence circuit having a pair of convergence coils coupled in series with the secondary of a transformer. Means are provided to apply a voltage pulse waveform at the horizontal repetition rate to the transformer and thereby develop a sawtooth current in the respective convergence coils. Means are also provided to apply a sawtooth voltage across the coil which when integrated in the coil develops parabolic currents. The combination of the parabolic currents and sawtooth currents provides the necessary magnetic field to converge the associated electron beams in a cathode ray tube. The secondary winding of the transformer which is used to supply the pulse voltage to the convergence coils has readily releasably connectors for coupling opposite leads of the secondary winding to the respective convergence coils. Pins are provided on the leads of the coils and these pins are received within the connectors. By reversing the points of coupling of the pins in the respective connectors, the direction of sawtooth current in the two convergence coils can be reversed. In this way, convergence is made possible in circumstances where the normal sawtooth amplitude adjustment devices could not accomplish convergence. The secondary winding of the transformer has a center tap which is coupled through a potentiometer to circuit ground. The center tap also has a connector which may receive either one of the pins associated with the leads of the respective convergence coils. In this way, the sawtooth level in either one of the coils may be substantially reduced to zero without affecting the level of sawtooth current in the other coil. As in the case of reversing the direction of current, this greatly extends the range of adjustment for the sawtooth current.

United States Patent [72] inventor Lawrence R. Poe! Eimhurlt, Ill. [21]Appl. No. 847,688 [22] Filed Aug. 5, 1969 [45] Patented Aug. 31, 1971[73] Assignee Admiral Corporation Chicago, 111.

[54] HORIZONTAL CONVERGENCE CIRCUIT 7 Clahns, 3 Drawhg Figs.

[52] U.S.Cl. 315/13 C [5 1] Int. Cl. 1101,]29/511 [50] FieldofSearch315/13C [56] Reference Cited UNITED STATES PATENTS 3.163,797 12/ 1964Singleback 315/13 C 3,414,758 12/1968 Grue 315/13 (C) 3,419,748 12/1968Neal et al.. 315/13 (C) 3,419,749 12/1968 Gerstein 315/13 (C) 3,447,0255/1969 Kool 315/13 (C) Primary Examiner-Malcolm F. HublerAttorneyl-Iill, Sherman, Meroni, Gross & Simpson ABSTRACT: A horizontalconvergence circuit having a pair of convergence coils coupled in serieswith the secondary of a transformer. Means are provided to apply avoltage pulse waveform at the horizontal repetition rate to thetransformer and thereby develop a sawtooth current in the respectiveconvergence coils. Means are also provided to apply a sawtooth voltageacross the coil which when integrated in the coil develops paraboliccurrents. The combinafion of the parabolic currents and sawtoothcurrents provides the necessary magnetic field to converge theassociated electron beams in a cathode ray tube. The secondary windingof the transformer which is used to supply the pulse voltage to theconvergence coils has readily releasably connectors for couplingopposite leads of the secondary winding to the respective convergencecoils. Pins are provided on the leads of the coils and these pins arereceived within the connectors. By reversing the points of coupling ofthe pins in the respectiye connectors, the direction of sawtooth currentin the two convergence coils can be reversed. In this way, convergenceis made possible in circumstances where the normal sawtooth amplitudeadjustment devices could not accomplish convergence. The secondarywinding of the transformer has a center tap which is coupled through apotentiometer to circuit ground. The center tap also has a connectorwhich may receive either one of the pins associated with the leads ofthe respective convergence coils. In this way, the sawtooth level ineither one of the coils may be substantially reduced to zero withoutaffecting the level of sawtooth current in the other coil. As in thecase of reversing the direction of current, this greatly extends therange of adjustment for the sawtooth current.

PATENTEU AUGBI Inn INVIiN'lOR.

HORIZONTAL CONVERGENCE CIRCUIT BACKGROUND OF THE INVENTION It has beenfound that a generally parabolic current is preferable for developingtherequired magnetic field in a convergence coil to converge a pluralityof beams in a cathode ray tube. It has also been found, however, thatimproved convergence results by adding a sawtooth current to theparabolic waveform thereby to provide a tilted parabola. The amount oftilt required depends on the geometric configurations of the tube and ofthe various windings mounted on the. tube.

Prior art circuits have provided means for adjusting the level of thesawtooth current within the convergence coils in order to accomplish thedesired amount of tilt. These prior circuits provide both a masteramplitude control which increases and decreases the level of sawtooth ina pair of coils and a differential control which increases the level inone coil while simultaneously decreasing the level of sawtooth in theother coil.

However, it has been found that in a number of production tubes, thesenormal controls are inadequate to produce the desired convergence.

Accordingly, the present invention has been accomplished to greatlyincrease the range of the normal sawtooth current adjustment controls.

Field of the Invention The field of art to which this invention pertainsis convergence circuits for color television receiversand in particularto convergence circuits for adjusting the sawtooth current in a pair ofseriesconnected convergence coils to control the convergance of a pairof electron beams.

SUMMARY OF THE INVENTION It is an important feature of the presentinvention to provide an improved convergence circuit for a colortelevision receiver.

It is another feature of the present invention toprovide extended rangefor the adjustment controls which regulate the sawtooth current inconvergence coils of a color television receiver.

It is an important object of the present invention to provide aconvergence circuit for a color television receiver which has means forreadily reversing the direction of the sawtooth current in a pair ofseries connected convergence coils.

It is an object of the present invention to provide a convergencecircuit having a pair of convergence coils coupled in series with thesecondary winding of a transformer wherein the transformer is the sourceof sawtooth current for the coils and wherein the leads of the.transformer are readily releasably coupled to the leads of theconvergence coils and are interchangeable.

It is another object of the present invention to provide a convergencecircuit as described above wherein the transformer which supplies pulsevoltages to the coils has readily releaseable meansfor being coupled toeither one of the leads of the convergence coils.

It is a further object of the present invention to provide circuit meansin a color television convergence circuit for substantially reducing thesawtooth current in one of a pair of series connected convergence coilswithout substantially affecting the sawtooth current in the other coiland in addition to provide selectable means for reversing the directionof the sawtooth current in the other coil.

These and other objects, features and advantages of the invention willbe readily apparent fromthe following description of a certain preferredembodiment thereof, taken in conjunction with the accompanying drawing,although variations and modifications may be efi'ected without departingfrom the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic of a convergencecircuit according to the present invention showing a pair of convergencecoils coupled in series with a transformer which supplies pulse voltagesto the coil and showing the readily releasable pin connectors on theleads of the coils and on the leads of the transformer, and in additionshowing a pin connector on the center tap of the transformer secondarywinding.

FIG. 2 is a portion of the schematic of FIG. 1 showing the pin lead ofone of the convergence coils coupled to the pin connector at the centertap of the transformer secondary winding.

FIG. 3 is a schematic similar to FIG. 2 showing the pin lead of theother convergence coil coupled to the center tap pin connector therebyeliminating the sawtooth correction for that coil.

DESCRIPTION OF THE PREFERRED EMBODIMENT The horizontal convergencecircuit of the present invention utilizes a pair of convergence coilscoupled in series with the secondary'winding of a transformer. Thetransformer has a pulse voltage applied thereto from the horizontaloutput transformer at 15.75 kHz.

The pulse waveform developed across the secondary of the transformer isintegrated in the convergence coils to develop a sawtooth current. Thissawtooth current is utilized as one of the two convergence waveforms.

The main convergence waveform is a parabolic current and is developedfrom the horizontal output transformer as well.

The voltage pulse information is coupled from the horizontal outputtransformer to a variable inductor which is also coupled in seriesrelationship with the two convergence coils. The pulse waveform isintegrated in an integrating circuit to develop a sawtooth voltage. Thesawtooth voltage is then applied across the convergence coils and isagain integrated to develop a parabolic current in the coils. Thecombination of the parabolic and sawtooth currents then provides therequired convergence information for the tube.

The circuit of the present invention provides means for adjusting theamplitudes of the parabolic and sawtooth currents, and also providesmeans for adjusting the relative magnitude of these waveforms in theirrespective coils. In other words, means are provided to adjust theoverall amplitude in both coils simultaneously, or to increase theamplitude in one coil and, at the same time, decrease the amplitude inthe other coil. These controls may be referred to as master amplitudeand differential amplitude controls respectively.

Since each picture tube is different in the particulars of the geometricconfiguration and the manner in which the respective coils are mountedon the tube, the master amplitude and differential amplitude controlsmust be adjustable in order to accommodate the specific differences ineach production item.

However, it has been found that in normal production runs, thevariations between tubes may be greater than the amount of availableadjustment in a typical convergence circuit. In other words, the masteramplitude and differential amplitude controls may be insufficient toaccommodateall picture tube situations. The result is that convergencecannot be achieved in certain tubes by adjusting the normal controls.

The present invention provides a means to greatly extend the range ofthe normal convergence controls and to provide a means for accomplishingconvergence in tubes where this was not possible with prior circuits.

The present invention provides readily releaseable couplings between thetransformer and the series connected convergence coils. These couplingstake the form of pin connectors and pin leads on the convergence coils.By providing these readily releaseable couplings, the direction of thesawtooth current through the coils can be reversed simply byinterchanging the points of connection of the convergence coils with thesecondary of the transformer. For instance, the pin lead for the greenconvergence coil can be inserted in the pin connector normallyassociated with the red convergence coil and vice versa.

In addition, the present invention provides a pin connector at thecenter tap of the transformer. The center tap is normally coupledthrough a variable impedance to circuit ground. By providing the pinconnection at the center tap, either of the convergence coil leads canbe coupled to the center tap to reduce the sawtooth current in thatrespective coil to substantially zero. To provide convergance, it may benecessary to eliminate the sawtooth correction in one of the convergencecoils without interfering with that correction in the other coil.

Also, by the present invention any of the above mentioned combination ofcircumstances can be utilized. For instance, one of the convergence pinscan be coupled to the center tap, while the other convergence pin can beinterchanged. As will be explained, a total of six possible combinationsof orientations and magnitudes for the sawtooth current can be obtainedby the pin connections to the convergence coils of the presentinvention.

Referring to the drawings in greater detail, a horizontal convergencecircuit according to the present invention is indicated generally by thereference numeral 10. The circuit includes a pair of convergence coil 11and 12. The coil 11 may be associated with the electron beam forexposing the green phosphor dots, while the coil 12 may be associatedwith the beam for exposing the red phosphor dots on the cathode raytube.

As explained, the coils 1 l and 12 are supplied with parabolic andsawtooth current waveforms to accomplish the desired convergencefunction. The energy supplied for these two waveforms is derived fromthe horizontal output transformer and is applied to a circuit point 13in the form of pulse information as indicated at 14. The pulseinformation as a repetition rate of 15.75 kHz.

The voltage pulse waveform is coupled from the circuit point 13 througha coupling capacitor 15 and a variable inductor 16 to a center tap 17 ona fiirther variable inductor 18. The inductor 18 has an adjustable core19 for varying the impedance between the upper and lower portions of thecoil 18.

The inductor 18 integrates the pulse waveform to develop a sawtoothcurrent which is then applied through a resistor 20 to an integratingcircuit including first and second capacitors 21 and 22 and a resistor23. A substantially sawtooth voltage is applied across the branch whichincludes the elements 21, 22 and 23. This sawtooth voltage is thenapplied to the convergence coils 11 and 12. The sawtooth voltage isintegrated in the coils 11 and 12 to develop a parabolic current.

A further branch is coupled in parallel with the integrating branch 21,22 and 23. The further branch includes a pair of resistors 24 and 25 anda pair of diodes 26 and 27. The resistor 23 has a variable contact 28which is grounded as at 29 and which is coupled to the anodes at 30between the two diodes 26 and 27. The diodes 26 and 27 are used to fixthe base of the parabola to a DC reference level to assure properconvergence.

The parabolic current applied to the convergence coils 11 and 12 thenproduces a magnetic field in the U-shaped cores 31 and 32 in a wellunderstood manner.

To develop the sawtooth current required in the convergence coils 11 and12, the pulse voltage 14 is coupled from a circuit point 33 through aline 34, a capacitor 35 and a further line 36 to a primary winding 37 ofa transformer 38.

The pulse voltage is then coupled by means of a movable core 39 to asecondary winding 40 of the transformer. The output of the primarywinding 37 in then coupled by way of a line 41 to the blue convergencecircuit.

The pulse voltage as developed across the secondary winding 40 of thetransformer 38 is integrated in the convergence coils 31 and 32 todevelop the required sawtooth current.

The overall magnitude of this sawtooth current may be adjusted byvarying a potentiometer 42 which is coupled from a center tap 43 on thewinding 40 to circuit ground at 44 through a resistor 45.

The differential amplitude of the sawtooth current through theconvergence coils 11 and 12 may be varied by adjusting the movablecontact 28 on the resistor 23. This will increase the sawtooth currentthrough one coil and simultaneously decrease the sawtooth currentthrough the other coil. In a similar manner, the variable inductor 16acts as a master amplitude control for the parabolic current in thecoils l1 and 12, while the variable inductor l9 acts as a differentialcontrol for the parabolic current.

Due to differences in the physical characteristics of production picturetubes and the various windings which are mounted to the tube, theadjustment controls 42 and 28 may be inadequate to produce the requiredtilt in the parabolic current in order to accomplish convergence. Inother words, the variations from tube to tube in the production line mayexceed the normal range of the convergence adjustment controls for thesawtooth waveform.

It has been found that the range of these controls can be significantlyextended by the present invention which utilizes three pin connectors46, 47 and 48. The pin connectors 46, 47 and 48 include pins 49 and 50which are coupled to the respective leads of the convergence coils 11and 12 and connectors 51, 52 and 53 which are adapted to receive thepine 49 and 50.

Any one of the connectors 51, 52 and 53 may receive either one of thepins 49 and 50. This provides a total of six combinations for couplingthe pulse voltage to the convergence coils.

For instance, in the position shown in FIG. 1, the sawtooth current willexist in one direction through the convergence coils 11 and 12. If thepins 49 and 50 are interchanged as shown by the dotted lines 54 and 55,the current through the coils 11 and 12 will be reversed.

FIGS. 2 and 3 are substantially identical to FIG. 1 and accordinglyreference numerals have been carried to FIGS 2 and 3 from FIG. 1.

FIG. 2 shows two additional combinations of the available possiblecouplings for the transformer winding 40 to the convergence coils 11 and12. In FIG. 2, the pin 50 is shown coupled to the connector 53. Thisarrangement, effectively reduces the sawtooth current in the coil 12 tozero without substantially altering the sawtooth current in theconvergence coil 11. In the alternative, the pin 50 may be coupled tothe connector 53, but the pin 49 can be coupled to the connector 52 toreverse the direction of sawtooth current in the winding 11.

FIG. 3 shows two additional combinations of the pin connections providedby the present invention. In FIG. 3 the pin 49 is shown received withinthe connector 48, thereby reducing the sawtooth current in the coil 1 1to substantially zero. In the alternative, the pin 50 which is shownreceived within the connector 52 may be received within the connector 51thereby reversing the sawtooth current in he convergence coil 12.

Accordingly, six combinations of pin and connector arrangements can beachieved by the present invention to significantly alter the nature ofthe sawtooth current within the convergence windings 11 and 12 therebyextending the range of the normal control adjustments 28 and 42.

I claim as my invention:

1. A horizontal convergence circuit comprising:

first and second convergence coils for converging a number of electronbeams in a cathode ray tube, means for supplying selected amplitudes ofparabolic and sawtooth current to said convergence coils, and means forselectably reversing the direction of sawtooth current in one of saidconvergence coils.

2. A horizontal convergence circuit in accordance with claim 1 whereinmeans are provided for selectably reversing the direction of current inboth of said convergence coils.

3. A horizontal convergence circuit comprising:

a transformer,

first and second convergence coils,

means for coupling substantial pulse voltage to said transformer,

readily interchangeable connector means for coupling and uncoupling saidconvergence coils in series with said transformer to allow the polarityof said pulse voltage to be reversed upon interchanging the points ofconnection of said convergence coils with said transformer.

4. A horizontal convergence circuit in accordance with claim 3 whereinsaid transformer has a center tap, an impedance coupling said center tapto circuit ground, and the point of coupling of said impedance to saidcenter tap being provided with coupling means which are interchangeablewith said connector means for said convergence coils.

5. A horizontal convergence circuit in accordance with claim 4 whereinsaid impedance comprises a resistance and wherein said resistance has amovable contact to provide a master tilt control for said convergencecoils.

6. A horizontal convergence circuit in accordance with claim 3 whereinsaid readily interchangeable connector means comprise pins andassociated pin connectors, said pin connectors being provided onopposite ends of the secondary winding of said transformer, and said oneof said pins being provided on a lead of each of said convergence coils.

7. A horizontal convergence circuit in accordance with claim 6 whereinan additional one of said pin connectors is coupled to the center tap ofsaid secondary winding and wherein a variable impedance is coupled fromsaid center tap to circuit ground to provide a master tilt control forsaid convergence coils, said additional pin connector being suitablyformed and positioned to receive another one of said pins from saidconvergence coils thereon.

1. A horizontal convergence circuit comprising: first and second convergence coils for converging a number of electron beams in a cathode ray tube, means for supplying selected amplitudes of parabolic and sawtooth current to said convergence coils, and means for selectably reversing the direction of sawtooth current in one of said convergence coils.
 2. A horizontal convergence circuit in accordance with claim 1 wherein means are provided for selectably reversing the direction of current in both of said convergence coils.
 3. A horizontal convergence circuit comprising: a transformer, first and second convergence coils, means for coupling substantial pulse voltage to said transformer, readily interchangeable connector means for coupling and uncoupling said convergence coils in series with said transformer to allow the polarity of said pulse voltage to be reversed upon interchanging the points of connection of said convergence coils with said transformer.
 4. A horizontal convergence circuit in accordance with claim 3 wherein said transformer has a center tap, an impedance coupling said center tap to circuit ground, and the point of coupling of said impedance to said center tap being provided with coupling means which are interchangeable with said connector means for said convergence coils.
 5. A horizontal convergence circuit in accordance with claim 4 wherein said impedance comprises a resistance and wherein said resistance has a movable contact to provide a master tilt control for said convergence coils.
 6. A horizontal convergence circuit in accordance with claim 3 wherein said readily interchangeable connector means comprise pins and associated pin connectors, said pin connectors being provided on opposite ends of the secondary winding of said transformer, and said one of said pins being provided on a lead of each of said convergence coils.
 7. A horizontal convergence circuit in accordance with claim 6 wherein an additional one of said pin connectors is coupled to the center tap of said secondary winding and wherein a variable impedance is coupled from said center tap to circuit ground to provide a master tilt control for said convergence coils, said additional pin connector being suitably formed and positioned to receive another one of said pins from said convergence coils thereon. 